Some Developments in Astronomy

• Eratosthenes (Greek)
  Measures earth's circumfrence

• Ptolemy (Egyptian)
  Wrote Almagest astronomical compenduim
  Developed system of Epicycles to "explain" retrograde planetary motion

• Nicolas Copernicus (Polish)
  His book On the Revolution of Heavenly Bodies argued the sun, not the earth, wes the center of the "universe"

• Galilio (italian)
  Developed laws of falling bodies
  Tested telescope to make sure it did not deceive him
  Used telescope to look at the heavens
  Discovers largest 4 moons of Jupiter

• Tycho Brahe
  Sets up observatory at Hven; records data

• Johannes Kepler (German)
  Uses Tycho's Data to surmise 3 laws of planetary motion

• Issac Newton (English)
  Extrapolated the work of Brahe and Kepler by:
  Inventing calculus (using "dot" notation for motion with respect to time)
  using calculus to develop his laws of mechanics
  basically force = sum of mass times acceleration
  Newton believed Time was absolute, but Space was not

• Leibnitz (German) Is also thought to have invented caluclus at about the sme time
  his notation was dx/dy, which was more general, since it allowed change of any variable withrespect to any other varible, not just time

• Einstein (German)
  As science progressed, it was found that Newton's Laws did not give the right answers under certain circumstances
  It did not work for objects moving very fast, nor for vert small particles
  Einstein Believed time is not absolute due to the behavior of light; space is also not absolute
  Einstein's theories worked better for objects moving very fast the two theories were:
  Special Theory of Relativity: Speed of light constant; as material objects approach the speed of light, tehy become more masive and shorter
  Traveling at the speed of light, a material object would have infinite mass and zero length.
  General Theory of Relativity: Gravity is the curvature of space
  the discrepancy for very small particles finally lead to the develpmentof the theory of Quantum Mechanics

• Charles Messier (French)
  comet hunter that developes a catalog of "nebula" that are not comets. Hence, Messier's Catalogue

• William Hershel
  Father of observational astronomy in the US
  Discovered Uranus
  Expanded Messier's catalogue to create the New General Catalog; hence NGC catalogue

• Emanual Kant
  speculates that some nebula may be external star systems

• Aurthur Eddington
  speculates stars energy ma come from nuclear processes

• Vesto Slipher
  Worked for Percival Lowell
  Obtained first evidence of doplar shifts in galaxies
  since no one knew distances, he did not know what thos meant (that they were moving)

• Edwin Hubble
  Discovered distance of Andromedia Nebula by measuring period of Cephiad variables within it
  This distance showed the Andromedia Nebula was a full fledged galaxie
  Formulated Hubbles Law of receeding objects

• Carl Jansky of Bell Labs
  Discovers "Galactic Noise" which became the basis of modern radio astronomy

• Harlow Shapely
  Established shape of Milky Way galaxie as a flat disc
  Thought the Milky Way was the whole universe

• Walter Baade
  Discovered stars fall into 2 groups:
  Old Red (no heavy elements) and Young Blue (lots of heavy elements)

• Carl Sandage
  Wrote popular book of astronomical history: Lonely Hearts of the Cosmos

• John Wheeler
  Coined term "Black Hole"